Limiting environmental factors

Limiting ennvironmental factors are factors whose presence or absence causes the growth of aquatic plants and/or algae to be restricted. A few examples are described below.

Suspended solids (tiny particles stirred up from bottom sediments or washed in from the watershed) can reach concentrations high enough that the growth of plants and algae is limited because sunlight is blocked out of the water column. This is a common situation in shallow lakes, especially those with heavy wave action like Lake Okeechobee in south Florida.
The color of dissolved substances, though translucent, can block sunlight and retard algal and plant growth. Many of Florida's lakes are tea-colored (reddish or reddish-brown) because of dissolved organic substances in the water. Even when tea-colored lakes are rich in nutrients, the growth of algae and submersed aquatic plants can be limited because the colored water prevents sunlight from reaching them.
Hydraulic flushing rate is the rate at which water in a waterbody is replaced with new water. The flushing rate can influence algal abundance significantly. Waterbodies with high flushing rates - such as many Florida springs - have low planktonic algal levels even though they may have high nutrient concentrations. This paradoxical condition exists because algae are flushed out of the system before they have time to grow to their maximum potential.
Aquatic macrophytes should also be considered as a limiting environmental factor because their presence may limit the growth of free-floating algae in Florida waterbodies indirectly. For example, if macrophyte coverage (PAC) is less than 30% of a waterbody, the presence of macrophytes covering over 50% of their bottom area typically have reduced algal levels and clearer water.

One explanation is that either aquatic macrophytes, or perhaps algae attached to them, use the available phosophorus in the water, competing with the free-floating algae for this necessary nutrient.

Another explanation is that macrophytes anchor the nutrient-rich bottom sediments in place and buffer the action of wind, waves, and human effects, preventing re-suspension of nutrients into the water column that can stimulate algal growth.

These same macrophytes act as a third type of buffer by preventing wind and wave action from re-suspending the actual algal cells (and/or other suspended solids) into the water column. By preventing algal cells from re-entering the water column, the macrophytes (plants) inhibit any further algal growth, due to the fact that the algal cells are "lost" in the bottom sediments where they are denied the necessary light and nutrients required for growth.

Often the management of a waterbody is focused solely on the manipulation of nutrients as a strategy for controlling growth of algae and/or plants. However, a truly skilled manager will evaluate all the potentially limiting environmental factors and consider every possibility.

The information on this page was derived in part from the following publication of
Florida Lakewatch of the University of Florida Department of Fisheries and Aquatic Sciences.
This booklet may be downloaded in its entirety as a PDF file by clicking here.
Scroll down till you see the Circular 101 icon.

Vic Ramey is the editor.

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A collaboration of the Center for Aquatic and Invasive Plants, University of Florida, and the Invasive Plant Management Section of the Florida Fish and Wildlife Conservation Commission.